refactor(DP15): centralize sendStateEvent as-any cast in typed helper

Add a typed `sendStateEvent(mx, roomId, eventType, content, stateKey?)`
helper in utils/room.ts that mirrors the DP16 account-data helper pattern.
The SDK's typed `sendStateEvent` overload rejects the fork's custom
`StateEvent` enum values, so every call site cast arg 2 to `any` (which
also collapsed the content type). The single `as any` cast now lives inside
the helper; a generic `content: T extends object` keeps each call site's
content type checked.

Route all 32 `mx.sendStateEvent(..., StateEvent.X as any, ...)` casts across
20 files through the helper. The 2 dynamic-string casts in developer-tools
(SendRoomEvent, StateEventEditor) pass a runtime string, not an enum value,
so they stay as-is.

No behavior change.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/app/features/room/message/Message.tsx

@@ -54,6 +54,7 @@ import {
   getEventEdits,
   getMemberAvatarMxc,
   getMemberName,
+  sendStateEvent,
 } from '../../../utils/room';
 import { mxcUrlToHttp } from '../../../utils/matrix';
 import { messageAriaLabel } from '../../../utils/a11y';
@@ -428,7 +429,7 @@ export const MessagePinItem = as<
     if (!isPinned && eventId) {
       pinContent.pinned.push(eventId);
     }
-    mx.sendStateEvent(room.roomId, StateEvent.RoomPinnedEvents as any, pinContent);
+    sendStateEvent(mx, room.roomId, StateEvent.RoomPinnedEvents, pinContent);
     onClose?.();
   };